Joe Flacco threw two touchdown passes on Sunday as the Baltimore Ravens powered their way to their fourth consecutive win at the expense of the Houston Texans.

The 18th overall selection in this year's draft, Flacco completed 15-of-23 passes for 185 yards for the surprising Ravens (6-3), who climbed within one-half game of the first-place Pittsburgh Steelers in the AFC North.

The Ravens' stifling defence intercepted Sage Rosenfels four times. Two of those picks led to second-half touchdowns, as Baltimore erupted for 29 points after intermission, a second-half season high.

Ravens linebacker Ray Lewis picked off Rosenfels twice and cornerback Samari Rolle also hauled in an interception.

Baltimore's fourth interception, by defensive tackle Haloti Ngata, stymied a potential scoring drive for Houston in the first half.

The Ravens also produced a safety when Houston offensive lineman Duane Brown was called for holding in the end zone, giving Baltimore a 9-3 lead late in the first half.

The Ravens took control on the opening possession of the second half, marching 75 yards in 11 plays to open a 19-6 cushion.

Willis McGahee capped the drive with a 1-yard run at the 9:16 mark.

McGahee finished with 112 yards on 25 carries to pace Baltimore's bullish running game.

Baltimore scored on their second possession of the game, moving 77 yards in seven plays and scoring on Flacco's 43-yard pass to Yamon Figurs.

The Texans (3-6) were lethargic on offence in the first half, managing just a pair of field goals from Kris Brown.

Houston's only other score was a 60-yard touchdown pass from Rosenfels to Kevin Walter that pulled the Texans within 19-13 with 3:01 left in the third quarter.

But Baltimore immediately responded with a nine-play scoring drive that culminated with a 1-yard pass from Flacco to tight end Todd Heap.

Ravens reserve quarterback Troy Smith threw a 14-yard touchdown pass with 6:29 left and McGahee added a 4-yard insurance touchdown run with 4:37 remaining.